How a car engine works Part 4

So you go out one morning and your engine will turn over but itwon't start... What could be wrong? Now that you know how an engineworks, you can understand the basic things that can keep an engine fromrunning. Three fundamental things can happen: a bad fuel mix, lack of compression or lack of spark.Beyond that, thousands of minor things can create problems, but theseare the "big three." Based on the simple engine we have beendiscussing, here is a quick rundown on how these problems affect yourengine:

The intake or exhaust valves are not sealing properly, again allowing a leak during compression.

There is a hole in the cylinder.

The most common "hole" in a cylinder occurs where the top of the cylinder (holding the valves and spark plug and also known as the cylinder head) attaches to the cylinder itself. Generally, the cylinder and the cylinder head bolt together with a thin gasket pressed between them to ensure a good seal. If the gasket breaks down, small holes develop between the cylinder and the cylinder head, and these holes cause leaks.

Lack of spark - The spark might be nonexistent or weak for a number of reasons:

If your spark plug or the wire leading to it is worn out, the spark will be weak.

If the wire is cut or missing, or if the system that sends a spark down the wire is not working properly, there will be no spark.

If the spark occurs either too early or too late in the cycle (i.e. if the ignition timing is off), the fuel will not ignite at the right time, and this can cause all sorts of problems.